Measurement of main circuit voltages, currents and powers
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PRECAUTIONS FOR MAINTENANCE AND INSPECTION
5.2 Measurement of main circuit voltages,
currents and powers
Since the voltages and currents on the inverter power supply and output sides include harmonics, measurement data
depends on the instruments used and circuits measured.
When instruments for commercial frequency are used for measurement, measure the following circuits with the instruments
given on the next page.
• When installing meters etc. on the inverter output side
When the wiring length between the inverter and the motor is large, the meters and CTs may generate heat due to line-to-line
leakage current. Therefore, choose the equipment which has enough allowance for the current rating.
To measure and display the output voltage and output current of the inverter, it is recommended to use terminal AM and FM/
CA output functions of the inverter.
Examples of measuring points and instruments
+-
Ar
As
At
Vr
Vs
Vt
Au
Av
Aw
Vu
Vv
Vw
W21
V
U
V
W
Inverter/
converter unit
Three-phase
power supply
To the motor
Instrument
types
Input voltage
Input current
Output voltage
Output current
: Moving-iron type
: Electrodynamometer type
: Moving-coil type
: Rectifier type
R/L1
S/L2
T/L3
P/+
N/-
W11
W12
W13
W22
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